concoction n.

word-forming element meaning "together, with," sometimes merely intensive; it is the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.

Proto-Indo-European root meaning "to cook, ripen." 

It forms all or part of: apricot; biscuit; charcuterie; concoct; concoction; cook; cuisine; culinary; decoct; decoction; drupe; dyspepsia; dyspeptic; eupeptic; kiln; kitchen; peptic; peptide; peptone; precocious; pumpkin; ricotta; terra-cotta.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pakvah "cooked, ripe;" Avestan -paka- "cooked;" Greek peptein "to cook, ripen, digest," pepon "ripe;" Latin coquere "to cook, prepare food, ripen, digest, turn over in the mind," Oscan popina "kitchen;" Lithuanian kepti "to bake, roast;" Old Church Slavonic pecenu "roasted;" Welsh poeth "cooked, baked, hot."